The 7950 and 7970 are along the expense of a 580 and 6990 at the moment; so that's just outright pointless.
He can wait around for the 78xx if he wants but who knows where that's going to lie on the hierarchy. As for the rethinking bit: unnecessary - MSI has a Z68 board that supports both SLI and Crossfire.
If possible go for a single card even for a few pounds more.
I'm running a SLI system for a while now, and I can tell you a few reasons why YES and why NO.
The NO is first the power consumption as earlier said, not so important for your bill but for the choice of PSU. With two Fermi chip Nvidia cards and a little hardware around them, you should have a minimum of 750W to start with.
Second, not all games support SLI properly, that's why you don't have, in every game the full power. With a single card more likely.
And third, the micro twitching. Which can happen on some setups and looks like very nervous lagging.
The YES is a little bit the price and upgrade ability with maybe one more card later on.
But you should select a proper mainboard for SLI (in my case ASUS), with a good intel chipset or if you go for AMD with Nforce chipset.
No Problem.
I don't say, that SLI is bad in general, but there are a lot things to consider.
And if you anyways start from scratch, a single GPU setup with the option for SLI/Crossfire is the best solution.
When you have a setup that you would consider, just post it here (MB, RAM, CPU, GPU and PSU, case also if you want) and I will give you my opinion for it. Only if you like![]()